Peers this week called for large employers to be legally required to investigate claims made by whistleblowers - in the wake of the Post Office scandal and the collapse of outsourcing firm Carillion. Campaigners say a gap in the law has allowed some of the UK's biggest scandals to escalate. Labour's Lord Wills, who was a justice minister under Gordon Brown tabled an amendment to the Employment Rights Bill based on work by whistleblowing charity Protect. If accepted by the Government, employers with a turnover of more than £10m would have duty to look into whistleblowers' concerns. Lord Wills is backed by former Tory education secretary Baroness Nicky Morgan, Lib Dem Baroness Kramer, and the Green Party's Baroness Jones. Protect chief executive Liz Gardiner said: "Whistleblowing has always been a cross-party issue, because it is good for workers and good for business. “This amendment is a cross-party push - with support from big names in the House of Lords - to get employers to do the right thing. It would involve minimal administration. “We urge the government to accept the amendment." The amendment already received backing when the Bill was passing through the House of Commons . Alex Sobel, a senior Labour backbencher, spoke in favour of a duty to investigate, backed by Liberal Democrat grandee Alistair Carmichael. Campaigners have long expected the best chance of success to be in the House of Lords, because of the chamber’s legal expertise. Sobel said: “The case for this amendment was made in the Commons and it must be settled in the Lords. Whistleblowers risk so much and they must be provided with basic protections, such as a duty for larger employers to investigate.” It's also seen support from outside Westminster, including from Azeem Rafiq , who exposed racism in cricket , and Michael Woodford who exposed Olympus accounting fraud.